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ID~ JUN 27'95 15:13 No .005 P.05 <br />• <br />':. T 1 I j !J i n ILlI : ~' ~. !~ mQ: w i 4 }:: 1 4 <br />Mr. kut Kluksd:dd <br />November 11, 19r1~i <br />I~al;c K <br />additional voluroc of water wily increase the size of the free water pad w the limits shown on <br />Figure 1. As shown on Lhis Figure, the 1 Wye storm and maximum olx:rating free water pool <br />will reach an elevation of 8577.3 at a disWtce of approximately 55U fl from the raix <br />embankment. Approxintattay 7.7 ft of additional storage is available prior to the free water pncd <br />rcacl»ng the raise. <br />'I'hr+ fivision fuuher reyuitcs the installation of 10 standpipe piezomcten; 5 al the crest of the <br />raise screened at the bast of the raise fill and 5 at the upstream toe of the raise which will be <br />surrounded by tailings as the tailings deposition continues. We are txmccrned about the quality <br />and interpretation of data which will be obtaint~ fmm the five tailings piczontcters. Obviously, <br />as tailings are deposited around the screened interval solution will cnlhxt in rho picumtca~r. <br />'I'bis water will have to be cvacuatul periodically for the picutmclers to provide any useful data. <br />Duce the screen saaion is crnnpletely buried by tailings, the piezometers will likely colla;t small <br />amoums of water as the adjatx:nt tailings consolidate. As there will be no way to determine <br />what tailings layer the water is coming from or what tailings thickness is invulveQ, we do not <br />Ix~licve that these piezancacrs will provide meaningful data for construction of the second dam <br />raise. Furtheflnore, the picwmeters would provide absolutely no data on the density, and <br />thcrefon~ undraincd shear surng;th or steadystate strength, of the water bt~tring layers which Gait <br />Lc in_corlxtratul into an anal~cis of stability of the second raise. A more t'igorous RaisC 2 lift <br />foundation investigation, as mcutioned in the f)ivision's teller, will define the saturttion <br />amdi-ions much more accuratcl~that the tailings piczometnrs. <br />'!'hc•. I )ivisiat has rayucxtul that BMltl demonstrate shat the revised raise fill plarcment method, <br />which has invoh~ed a sin{;Ic lift 4 fi thick and a typical lift thickness of 3 ft, results in matrriai <br />which meets the .epccificxl dogrcc of compaction throughout the entire 1iG thickness, 't'his has <br />bcxn and will ectntinuc to be conducted as part of the routine QA/AC: proeuiures. No failirtl; <br />density or relative dcgrlx: of compaction test results have been rrxorded to-date thmughout the <br />full lift thickness. <br />}tail l,intr <br />I'hr. Division has rsxlucstcxl a revision to the phase Ilphase Il coil liner tic-in which was adopted <br />during, ce+nstntctinn. As of the, dart: this request was received, the soil liner placement had been <br />cumplrkd and the. tic-in was fully covcrrxi with >ycomentbranc liner. As the tic-in prrxufurc. <br />arlup[ul provided for a hcUCr liner system than the approvui design and any attempts to mcxlify <br />the tic in :d this IxtiN in aloe would likely resuh in a .less effective IininE. system tluough <br />adrlitiunal construction traffic and geomembetne liner seams, we strongly rei~ummcnd against <br />